Koh Samui has three distinct seasons: the dry season (December to February), the hot season (March to August) and the rainy season (September to November).

With that in mind the months of December to February are usually considered the best time to visit (with average highs of around 30 degrees), although it remains peak season though to June, when highs can reach around 33 degrees. While October and November are the rainiest months, Koh Samui gets of much more light in comparison to mainland Thailand during this period, suffering significantly less rain.